Document U.S. Pat. No. 6,597,989 describes a satellite communication system optimized to ensure coverage over the elevated population areas of the North hemisphere. This system comprises a constellation of satellites in elliptical orbit with an apogee of less than 4000 km and is optimized to cover by priority the high population density geographical areas of the North hemisphere. This system is optimized to offer maximum capacity above 25° N of latitude and reduced capacity between 25° N and 50° S, which does not include the region of the South pole.
The document “Extension of mobile satellite communications to the polar regions” published in 1984 in the journal “Space communication and broadcasting 2” on pages 33 to 46, describes a constellation of satellites in low circular orbit inclined at 90°, the satellites being disposed at an altitude of between 1400 km and 1600 km, so as to ensure low-bitrate, intermittent mobile service in the L band over the polar areas delimited by the latitudes 70° North and 70° South. This system exhibits the drawback of not making it possible to ensure a high-bitrate service, nor of ensuring continuous service over the polar regions.
Documents U.S. Pat. No. 5,410,728 and U.S. Pat. No. 5,604,920 describe a constellation of 66 satellites distributed over 11 planes of an orbit inclined at 86.4° at the altitude of 781 km so as to ensure an L-band mobile service over a worldwide coverage including both poles. This system exhibits Ka-band feeder links to anchor stations. However, the capacity of the Ka-band resources is not sufficient over the poles to meet future requirements identified for 2020. In particular the high-bitrate-service capacity requirements are evaluated at 250 to 400 Mbps, at latitudes greater than 75° North and 4000 Mbps, at latitudes greater than 66° North.
Satellite communication systems also exist which comprise a constellation of satellites placed in very elliptical orbits, such as the Molniya or Toundra constellations, which make it possible to cover northern regions. However, these constellations exhibit an apogee situated at about 40000 km, thus giving rise to too considerable a unidirectional transit time, greater than 300 ms, and contributing to a degradation in the quality of service of the real-time communications with a terminal. Furthermore, these systems are optimized to offer a continuous service over just one of the two polar regions.